A switching hub and a wireless LAN (Local Area Network) access point are communication devices for relaying between networks. They are bridge devices which relay communications in the data link layer (layer 2). In addition, a router device relays communications in the network layer (layer 3). Currently, these devices are dedicated to relaying of communications, which means that they typically do not incorporate functions as storage. Meanwhile, the possibility of incorporating storage with communication devices is being investigated, with the advent of concepts such as ICN (Information Centric Networking), CCN (Content Centric Networking), edge computing, and fog computing.
By using CDN (Content Delivery Network), it is possible to distribute information widely through the Internet. In CDN, effective transmission of information is realized by placing a large number of cache servers in the network and transmitting information from the cache server which is closest to the terminal which issued a request. The cache server to use can be selected based on methods such as DNS or HTTP redirection.
By combining the abovementioned methods, it is possible to construct a CDN incorporating edge computing technology. By using CDN with edge computing technology, controlling the distribution of information and getting the history of the distribution, for small granularities are possible. Such tasks were difficult when conventional CDNs are used.
However, if conventional cache server selection methods are used, the successful selection of a cache server ready for edge computing is difficult. Since the number of communication devices installed in the edge network is very large, an enormous number of devices need to be taken into account. For example, in order to use the DNS-based selection method, a distributed database available from the entire Internet needs to be maintained. It is difficult to add and manage information on the workloads of the individual edge networks and caching devices to the above database. The situation is similar for cases when HTTP redirection is used. This is because DNS is also used to identify the HTTP server that issued the redirection.
If the cache server installed in the edge network were selected successfully, other problems still exist. If the cache server closest to the terminal which sent the request is always selected, there is a possibility that the requests concentrate in a specific cache server. In such cases, problems such as degraded I/O performance of the cache storage and exhaustion of the storage device may occur.